Patent Documents 1, 2 disclose a hydraulic braking system including: a pump device; a common passage connected to the pump device and brake cylinders provided for front left and right and rear left and right wheels; and a hydraulic pressure control valve device provided between the common passage and each of the brake cylinders.
In the hydraulic braking system disclosed in Patent Document 1, a bypass passage specific to air bleeding is further provided so as to directly connect between a discharge side of the pump device and a reservoir. Also, a bypass cut-off valve is provided, and when air bleeding is performed, the bypass cut-off valve is switched to an open state, and the pump device is actuated. Working fluid is pumped up from the reservoir and discharged by the pump and transferred to the reservoir via the bypass passage. As a result, air bleeding is performed for a passage between a suction side of the pump and the reservoir, the interior of the pump, and surroundings of a discharge opening of the pump, for example.
In the hydraulic braking system disclosed in Patent Document 2, the presence or absence of air in the hydraulic system including the brake cylinders is determined based on a state of change in hydraulic pressure in the brake cylinders.